W-CDMA has been standardized as a third generation cellular mobile communication scheme by 3GPP (3rd Generation Partnership Project), and services thereof have been sequentially provided. Further, HSDPA (High Speed Downlink Packet Access), which is a faster communication scheme, has been also standardized, and services thereof are about to be provided.
On the other hand, evolved universal terrestrial radio access (hereinafter, “EUTRA”) has been considered by 3GPP. OFDM (Orthogonal Frequency Division Multiplexing) has been considered as an EUTRA downlink. Additionally, DFT (Discrete Fourier Transform)-spread OFDM, which is a single-carrier communication scheme, has been considered as an EUTRA uplink.
FIG. 7 illustrates an EUTRA uplink and downlink channel configuration. An EUTRA downlink includes a DPiCH (Downlink Pilot Channel), a DSCH (Downlink Synchronization Channel), a PDSCH (Physical Downlink Shared Channel), a PDCCH (Physical Downlink Control Channel), and a CCPCH (Common Control Physical Channel).
An EUTRA uplink includes a UPiCH (Uplink Pilot Channel), an RACH (Random Access Channel), a PUSCH (Physical Uplink Shared Channel), and a PUCCH (Physical Uplink Control Channel) (see Non-Patent Documents 1 and 2).
FIG. 8 illustrates an example of an uplink radio resource configuration. In FIG. 8, horizontal and vertical axes denote time and frequency, respectively. FIG. 8 shows the configuration of one radio frame, and the radio frame is divided into multiple resource blocks. In this example, a resource block is a unit region defined by 1.5 MHz in the frequency direction and 1 ms in the time direction. RACHs, PUSCHs, and PUCCHs explained in FIG. 7 are allocated to the regions as shown.
In other words, a dot-hatched region, a non-hatched region, and a cross-hatched region denote resource blocks to which an RACH, a PUSCH, and a PUCCH are allocated, respectively.
An E-UTRA uplink RACH includes an asynchronous random access channel and a synchronous random access channel. The asynchronous random access channel uses the 1.25 MHz band as a minimum unit. A base station device prepares multiple random access channels for accesses from multiple mobile station devices. A main intended use of an asynchronous random access channel is to synchronize a base station device and mobile station devices. Additionally, a connection time can be reduced by transmitting a few bits of data, such as a scheduling request for radio resource allocation, using an asynchronous random access channel. An intended use of a synchronous random access is to transmit a scheduling request (see Non-Patent Document 2).
Asynchronous random access includes contention-based random access and non-contention-based random access. The contention-based random access is normal random access that might cause a contention among mobile station devices. The non-contention-based random access is random access that does not cause a contention among mobile station devices, and is performed under control of the base station device in a special case, such as a handover, for quickly synchronizing the base station device and mobile station devices.
In the asynchronous random access, only a preamble is transmitted for synchronization. This is called a random access preamble. This preamble includes a signature that is a signal pattern indicative of information. Several ten signatures are prepared, from which some signature is selected to express several bits of data. Currently, 6 bits of data is transmitted by a signature in EUTRA. For the 6 bits of data, 2 to the 6th power (i.e., 64) signatures are prepared.
A random ID is allocated to 5 bits of the 6 bits of the signature, and any one of random access reason, downlink path-loss/CQI (Channel Quality Indicator), and the like is allocated to the remaining 1 bit (see Non-Patent Document 3).
FIG. 9 is a procedure example of contention-based random access that is asynchronous random access. Firstly, a mobile station device selects a signature based on a random ID, downlink pass-loss/CQI information, or the like, and transmits a random access preamble on an asynchronous random access channel (message Ma1). Upon receiving the preamble from the mobile station device, the base station device calculates a synchronization timing shift between the mobile station device and the base station device based on the preamble to generate synchronization shift information. Additionally, the base station device performs scheduling for transmitting an L2/L3 (Layer 2/Layer 3) message to generate scheduling information and to assign a cell-radio network temporary identity (hereinafter, “temporary C-RNTI”).
The base station device allocates, to a PDCCH, an RA-RNTI (Random Access-Radio Network Temporary Identity) indicating that a random access response to the mobile station device having transmitted the preamble on the random access channel is allocated to the PDSCH. Further, the base station device transmits a random access response including the synchronization timing-shift information, scheduling information, the temporary C-RNTI, and the signature ID number (or random ID) of the received preamble in the resource block of the PDSCH on which the random access response allocation has been indicated by the RA-RNTI (message Ma2). The RA-RNTI is a specific value not used as the C-RNTI. The mobile station device detects the specific value, and thereby detects that the random access response is allocated to the PDSCH.
FIG. 10 is an example of a random access response allocated to a PDSCH when the allocation is indicated by an RA-RNTI. As shown in FIG. 10, if a random access response allocation is indicated by the RA-RNTI, random access response messages corresponding to multiple mobile station devices (n devices in the case of FIG. 10), each including synchronization timing-shift information, scheduling information, a temporary C-RNTI, and the signature ID number of the received preamble, can be included in one resource block of the PDSCH.
Upon confirming that the RA-RNTI is included in the PDCCH, the mobile station device confirms the information included in the random access responses included in the PDSCH. Then, the mobile station device extracts a response including the signature ID number (or random ID) of the transmitted preamble, and corrects the synchronization timing shift based on the synchronization timing shift information included in the extracted response. Then, based on the received scheduling information, the mobile station device transmits an L2/L3 message including at least the C-RNTI (or the temporary C-RNTI) in the scheduled resource block (message Ma3). Upon receiving the L2/L3 message from the mobile station device, the base station device transmits, to the mobile station device, a contention resolution for determining whether or not a contention among mobile station devices is occurring by using the C-RNTI (or temporary C-RNTI) included in the received L2/L3 message (message Ma4) (see Non-Patent Document 3).
FIG. 11 is an example of a procedure of non-contention-based random access that is asynchronous random access. Firstly, the base station device selects the signature ID number, and indicates a preamble assignment to the mobile station device on the PDSCH (message Mb1). The mobile station device transmits a random access preamble on an asynchronous random access channel by using the indicated signature ID number (message Mb2). Upon receiving the random access preamble from the mobile station device, the base station device calculates a synchronization timing shift between the mobile station device and the base station device based on the preamble. Then, the base station device allocates an RA-RNTI or a C-RNTI indicative of a response to the mobile station device to the PDCCH, and transmits a random access response including the synchronization timing-shift information on the PDSCH (message Mb3). The mobile station device corrects the synchronization timing shift based on the received random access response (see Non-Patent Document 3).
[Non-Patent Document 1] 3GPP TS (Technical Specification) 36.211, V1.10 (2007-05), Technical Specification Group Radio Access Network, Physical Channel and Modulation (Release 8)
[Non-Patent Document 2] 3GPP TS (Technical Specification) 36.212, V1.20 (2007-05), Technical Specification Group Radio Access Network, Multiplexing and channel coding (Release 8)
[Non-Patent Document 3] R2-072338 “Update on Mobility, Security, Random Access Procedure, etc,” 3GPP TSG RAN WG2 Meeting #58, Kobe, Japan, 7-11 May 2007